Gas lifting of granular solids as a dense mass



Aug. 27, 1957 GAS LIFTING Filed May 51. 195] H. c. PASSMORE 2,804,351

OF GRANULAR SOLIDS AS A DENSE MASS 2 Sheets-Sheet 1 Fig. 2

INVENTOR. HOWARD C PASSMORE ATTORNEYS 1957 H. c. PASSMORE 2,804,351

GAS LIFTING OF GRANULAR soLIDs AS A DENSE MASS Filed May 31. 1951 Y 2 Sheets-Sheet 2 INVDV TOR HOWARD C. PASS ATTORNEYS MbRE United States Patent GAS LIFTING OF GRANULAR SOLIDS AS A DENSE MASS Howard C. Passmore, Wallingford, Pa., assignor to Sun glil Company, Philadelphia, Pa., a corporation of New ersey Application May 31, 1951, Serial No. 229,117 17 claims. (Cl. 302-53 This inventionrelates to the elevation of granular solids by means of a lifting gas and more particularly to the elevation by means of a lifting gas of mixtures of granular solids, a major proportion of which are coarse granular solids which are too large to pass a 20 mesh U. S. Sieve Series screen.

Numerous industrial processes involve the continuous circulation of coarse granular solids through a process system. A particularly advantageous manner of effecting movement of the solids through the system is by gravitating the solids as a compact mass from a high level in the system to a low level therein and elevating the solids from the low level in the system by means of a lifting gas to a high level therein, for subsequent gravitation of the solids therefrom. An example of such a process system is the so-called moving bed catalytic conversion system employing a gas lift. In such systems, coarse granular contact material gravitates through a conversion zone and a regeneration zone in series, and upon reaching a low level in the system, is transported upwardly by means of a lifting gas to a high level in the system for subsequent gravitation therefrom, the operation being cyclic, with continuous circulation of contact material through the conversion zone and regeneration zone. 7

In the moving bed catalytic conversion system, and in other systems employing coarse granular solids, the solids employed are generally, as originally prepared, particles having size greater than 20 mesh in the U. S. Sieve Series scale. During passage of such particles through a solids circulation system, the particles undergo attrition and as a result substantial amounts of particles smaller than 20 mesh are formed. In stabilized operation, however, such smaller particles are removed from the system, and fresh larger particles added thereto,at rates sufiicient to maintain in the system a mixture of particles which contains a major proportion of particles which are too large to pass through a 20 mesh screen.

Previously, mixtures of solids as specified above have been elevated by means of a lifting gas in sparse phase lifting operations, wherein solids are suspended at a low level in relatively large quantities of lifting gas and carried thereby to a high level. Sparse phase lifting operations are characterized by relatively high velocities of solid particles as they are carried upwardly by the lifting gas, and also by low concentrations of solids in the lift conduit. These velocities are sufficiently high and the concentration sufiiciently low that in operation where lifting gas is being continuously introduced into the zone where suspension of solids in lifting gas occurs, if the supply of lifting gas to that zone be abruptly interrupted, the lift conduit will be less than one quarter full when the solids come to rest, the concentration of the solids in the lift conduit having been initially low, and many of the solids having by virtue of their high velocities issued from the top of the lift conduit after the gas supply was interrupted.

According to the present invention, a highly advantageous dense phase lifting of coarse granular solids is 2,84,351 Patented Aug. 27, 1957 provided. Such lifting is distinct from previous sparse phase lifting in that the dense phase type of operation employs relatively small quantities of lifting gas relative to the amount of solid lifted and provides a high concentration of solids in the lift conduit andlow velocities of solids therethrough. As a consequence, in a continuous dense phase lifting operation according to the present invention, if the supply of lifting gas is abruptly interrupted, the lift conduit will be more than half full, and in some cases entirely full, when the solids come to rest.

To achieve a dense phase lifting operation according to the present invention, lifting gas under elevated pressure is introduced into a lower portion of an elongated compact mass of coarse granular particles in a confined lifting zone. The lifting gas passes upwardly through the com pact mass, exerting levitating efifect on the particles and rendering them mobile, and issues from the compact mass into a relatively expanded zone after having passed through the entire length of the compact mass. The liftingv gas is passed through the compact mass at a rate sufficient to impart upward motion to the particles, but at a rate in suflicient to substantially entrain the coarse particles of the mixture, i. e. the particles which are too large to pass a 20 mesh screen. It is necessary to avoid substantial entrainment of coarse solids in order to prevent the initiation of a sparse phase lifting operation instead of the desired dense phase operation.

As the particles in the compact mass move upwardly, according to the present invention, additional particles under elevated pressure are continuously supplied to a lower portion of the compact mass from a supply Zone communicating with the confined lifting zone. Preferably, the additional particles are admixed with lifting gas, in the supply zone or subsequently to introduction thereinto, and are passed from the supply zoneinto the confined lifting zone as a substantially compact mass Such premixing of gas and solids before introduction into the lifting zone is advantageous in that it provides more uniform distribution of gas over the cross section of the dense mas of rising solids.

In operation according to the present invention, by first establishing an elongated compact mass in a confined lifting zone, e. g. by filling or partially filling an elongated lift conduit from the top with granular solids, and then introducing lifting gas into a lower portion of the compact mass, it is possible to achieve a dense phase lifting operation, whereas sparse phase lifting operations have been obtained by the prior art methods, wherein a supply vessel having a communicating lift conduit extending up wardly therefrom has been filled with catalyst, the lift conduit remaining substantially empty, and lifting gas introduced into the supply vessel to elevate solids therefrom by means of the lift conduit.

From the above it is seen that the starting-up conditions substantially determine the nature of the lifting operation. If an elongated compact mass of solids is established in the lift conduit, a dense phase lift can be obtained; otherwise a sparse phase lift is obtained.

The dense masses of granular solids which rise through confined lifting zones according to the invention are generally characterized by high bulk density, i. e. at a given moment the weight of solids in a unit volume of the confined zone is high. In a dense phase lifting operation, the bulk density of a rising dense mass of solids is generally greater than 0.5 times and frequently almost as great as the bulk density of a loosepacked compact bed of the same solids at rest, whereas in a sparse phase lifting operation, the bulk density of the same solids is much less, e. g. about 0.15 times the bulk density of a loosepacked stationary bed. The above bulk densities are given as examples; they vary with average particle size and size distribution and other factors.

The pressures at which lifting gas is supplied to a lower portion of an elongated compact mass of solids according to the present invention are high relative to the pressures employed in sparse phase lifting operations. Forcxam'ple, in alsparsepha'se lifting operation, the gas pressure at the bottom of a lift conduit 100'feet high mightbe five pounds per square inch gauge in order to overcome the lift pressure drop, whereas in a dense phase lifting operation, the gas pressure at the bottom of a lift conduit 100 feet high might be seventy pounds per square inch gauge to overcome the greater lift pressure drop. These pressures vary, however, with the other conditions in the respective operations. j

According to the present invention, lifting gas is supplied to a lower portion of an elongated compact mass of coarse granular solids in a confined zone. Preferably, the height of the mass of solids above the point of iintroduction of the gas is within the approximate range -400 times, more preferably 50-300 times, the average major dimension of the horizontal cross section of the lift conduit. In many commercial installations involv ing the circulationof coarse granular solids, the solids must b'e elevated through distances of more than a hundred fe et'. With a dense phase lift, as obtained accordingtothe present invention, the heightof rise of solids above the top of the lift conduit can be maintained at a small fraction of the height of rise necessarily obtained with a sparse phase lift. By height of rise is meant the maximum distance to which solids rise abovethe top of the lift conduit, when discharged into an open space above the top of the lift conduit, before reversing direction and falling down again. The advantage of a low height of rise is that the solids fall less far before striking a solids surface below the top of the lift conduit.

The greater the' distance of fall, the greater the attrition of the granular solids, and in many processes it is undesirable that attrition of the solids should occur to an excessive degree.

The present invention is applicable generally to granular solids in mixtures whereina major proportion is larger than 20 mesh; Preferably 'the solids are substantially free from particles having major dimension greater than one-half inch. Examples of solids to which the invention is advantageously" applied are granular catalysts such "assilica alumina cracking catalyst, and granular inert, refractory heat-transfer 'materials such as are frequently used in 'non catalytic hydrocarbon conversion processes. The solid' particles can beany suitable shape eJg. spherical or cylindrical or such intermediate shapes'asresulffrom attrition of cylindrical particles, etcL" Thep'res'ent invention, as applied to solids whichare subj to"substantial attrition upon striking solid surfafes, has the particularadvantage of minimizing such attrition. i

Lifting"gas used according to the present invention can beany suitable gas; "it cambe inert, chemically unreactive with the solids lifted, or it can be capable of undergoing a reaction uponcontact with the solids, as in the case of hydrocarbon vapors used to elevate contact material having the ability to promote a hydrocarbon conversion reaction. Examples of inert lifting gas which can be advantageously used to elevate contact material used in hydrocarbon conversionare steam, air, flue gas,

etc.

The invention .will be further described with reference to the accompanying drawings which illustrate apparatus I which can be "used in dense phase lifting operations according to the present invention. Figure 1 shows a solids circulation system including means according to the invention' whereby' granular solids under elevated pressure can be continuously introduced into the inlet of a lift conduit, andalso including particular apparatus associated, according to the invention, with the inlet to the lift conduit. Figures 2,3, and 4,show other types of apparatus which can, according to the invention, be associated with the inlet to the lift conduit. Figure 5 shows particular apparatus which can, according to the invention, be associated with the outlet from the lift conduit.

In Figure 1 there are shown: an upper reaction vessel 10, such as for example a catalytic cracking reactor; a lower reaction vessel 11, such as a catalytic cracking regenerator; pressuring vessels'12 and 13; engaging vessel 16; lift conduit 18; and disengaging vessel 19.

Lift conduit 18 has its lower end positioned within engaging vessel 16. Secured to the lower end of lift conduit 18 is one end of pipe bend 31, and secured to the other end of pipe bend 31 is short pipe section 32. Secured to the inner wall of vessel 16 is cylindrical channel 35.

Following is a description of one manner of operation which can be employed according to the invention, the

operation described including the starting-up period for a moving bed'catalytic conversion process. 'Particlcform solid contact material'can be initially introduced in'the following'mann'er into the apparatus'shown in Figure l: Sufficient contact material is mechanically couveyed to the top of lift conduit 18 to fill the latter from above; Pressuring' vessels 12 and 13 and engaging vessel 16 are filled through'manholes not shown, with contact material. Valves 25, 26 and 29 are closed, and valve 28 is opened, and lifting gas under elevated pressure is introduced into vessel 16 by wa'y of line 30 and channel 35 to build up thepressure in vessels 12 and 16 and to supply lifting gas under elevated pressure,'by way of pipe section. 32 and pipe bend '31, to the bottom of the compact mass of solids in lift conduit 18. Lifting gas thus supplied caus esthe solids to move upwardlyin a dense'inass thr'ou-ghlift conduit 18 and to issue from the top thereof 'into'disengager 19, in the bottom of which a compact mass of solids-collects and moves downwardly into and through line 21 and the apparatus therebeneath 'until it is stopped by closed valves 25 and 26 and collectsthereaboveas a compactmass.

I As solids flow from vessel16into and through'pipe section 32, pipe bend31, and 'lift conduit 18' insuccession', solids under elevated'pressure' flow from vessel 12 into vessel "16 to replenish the latter. When vessel 12 is nearly empty, valve 28is closed and valve '29is opened, whereupon lifting 'gas under pressure enters from vessel 16 into vessel 13 to pressure the latter. Solids then flow from vessel 13' into vessel16 to replenish the latter. Vessel 12 is then vented through means not shown, and additional solids are introduced thereinto, through a manholenot shown, to fill vessel 12. "When vessel 13iisn e'arly1ernpty, valve 29 is closed and valve 28 isopened',vessel.13 is vent ed and refilled with solids while vessel 12'supplies solids "to vessel 16. .Thiscyclic operation is continued, with vessels 12 and '13 lalter nately" supplying solids to'vessel 16, and the lattercontinuously supplying solids andli fting gas to lift conduit 18 and supplying lifting gas'to vessels 12 and 13 to pressure the'latter when necessary. l

The above operation iscontinued until'the entire systemof apparatus has been filled to the desired degree with solids. Then the operation is modified by introducing solids into the vessels 12 and 13 from regenerator 11 through lines 23 and 24' instead of through manhole as before. Thus, while vessel '12 fis'under elevated pressure and supplying solids to'vessels 16, valve 25 being closed, vessel 13 is underlesser pressure, having been vented, and receives solids through line 211. When vessel 12 is nearly empty of solids, valve 28 is closed and vessel 12 is vented. Then valve 25 is opened and valve26 is closed, so' that the continuous .fiow of solids from regenerator 11 isdiverted to vessel 12. .ValVe 29 is opened to admit lifting gas under pressure to vessel 12f: to pressure the latter. Then solids fiowfro'myessel 13 into'vessel 16 until vessel 13 is nearly-empty, whereupon valve 29 is closed, vessel 13 vented, valve 26 opened, valve 25 closed, and valve 28 opened to complete a cycle of operation.

In the above manner, circulation of solids through the entire system of apparatus is initiated, with solids gravitating from disengager 19 to vessel 16 and being lifted therefrom as a dense mass to disengager 19 again. The initiation of the hydrocarbon conversion reaction in reactor 18 and of the contact material regeneration in regenerator 11 can be accomplished in any suitable manner; e. g. hot air can be introduced into regenerator ll to heat the solids therein to a conversion temperature; then the heated solids can be circulated to the reactor to contact heated hydrocarbons introduced thereinto.

It is to be understood that, although in the above described operation, vessels 12 and 13 are pressured by lifting gas introduced from vessel 16 through lines 14 and 15, those vessels can according to the invention be pressured by lifting gas from any other suitable source.

The apparatus shown in Figure l, with the pressuring vessels 12 and 13 providing a plurality of containers for granular solids, is particularly advantageous for supplying solids under elevated pressure to engaging vessel 16, which in turn continuously introduces granular solids under elevated pressure to lift conduit 18. This apparatus makes it possible to withdraw solids continuously from a solids source such as the outlet of regenerator 11, at relatively low pressure, e. g. seven pounds per square inch gauge, pressure the withdrawn solids to a relatively high pressure, e. g. seventy pounds per square inch gauge, and continuously introduce the pressured solids into a lift conduit. In a preferred operation as described above, there is at all times a pressuring vessel at relatively low pressure into which solids are introduced from regenerator 11. This is a desirable feature, since it is usually harmful to the solids to remain stationary in the regenerator for a substantial period of time.

In the apparatus shown in Figure 1, a restricted hori zontal inlet to lift conduit 18 is provided at the lowest point of pipe bend 31, this inlet having a vertical cross sectional area approximately equal to the horizontal cross sectional area at the bottom of lift conduit 18. It is preferred that a restricted'horizontal inlet to the lift conduit be provided according to the invention. It is further preferred that such inlet have cross sectional area approximately equal to the horizontal cross sectional area at the bottom of the lift conduit 18.

. It is further preferred that a downflow conduit be used communicating through a closed connection with the horizontal inlet, no lifting gas being introduced into the lift conduit except by way of the downflow conduit. Such downflow conduit it provided in Figure l by pipe section 32 and that part of pipe bend 31 between pipe section 32 andthe lowest point of pipe bend 31. Such downflow conduit also preferably has cross sectional area approximately equal to the horizontal cross sectional area at the bottom of the lift conduit. Thevertical length of the downflow conduit can vary, and is preferably within the approximate range l-ZO time the major dimension of the horizontal cross section at the bottom of the lift conduit. The downflow conduit need not be vertical, so long as there is a sufficient vertical component to the downflow path. I

v The aboveedescribed features associated with the inlet tov the lift conduit are preferred according to the invention in thatthey tend to provide a smooth operation without substantial formation of lifting gas pockets in the rising dense mass, or any other undesirable condition.

Turning now to Figure 2: there are shown an engaging vessel 16, lift conduit 18, solids inlet line 33, gas inlet line 38, channel 35, cylindrical disk 36 spaced from the bottom of lift conduit 18, and rod 37 slidably mounted through. the bottom ofvessel 16 .andthrough packing gland 38. In operation, vessel 16 in Figure 2 receives downflow conduit.

solids through line 13 and lifting asander uev'ated ressure through line 30, similarly to vessel 16 inFigur'e 1. Lifting gas is introduced through the restricted space between disk 36 and the bottom of lift conduit 18 and is introduced into the bottom of the mass of solids in lift conduit 18. Lifting gas thus introduced causes the solids to rise in a dense mass through lift conduit 18, and more solids are continuously introduced under elevated pressure through the restricted space between disk 36 and the bottom of lift conduit 18 into the bottom of lift conduit 18.

In the apparatus shown in Figure 2, disk 36 has horizontal cross sectional area substantially greater than that of the bottom of lift conduit 18, and provides a restricted horizontal inlet to lift conduit 18, i. e. restricted horizontal. passage for solids and gas between its upper surface and the bottom of the wall of lift conduit 18. The above passage has a degree of restriction which is adjustable by vertical movement of rod 37 and disk 36; In the light of the present specification, a person skilled in the art can make the proper adjustment to provide a smoothly operating dense phase lift.

Turning now to Figure 3: there is shown an engaging vessel 16, lift conduit 18, pipe bend 34, solids inlet line 33, and gas inlet line 31). In operation, vessel 16 receives solids through line 33 and lifting gas under elevated pressure through line 30. Lifting gas is introduced through the mass of solids in vessel 16 into and through the mass of solids in pipe bend 34, and is introduced into the bottom of lift conduit 18. Lifting gas thus introduced causes the solids to rise in a dense mass through lift conduit 18, and more solids are continuously introduced under elevated pressure through pipe bend 34 into the bottom of lift conduit 18.

The apparatus in Figure 3 and operation thereof differs from that in Figure l in that the pipe bend communicating through a closed connection with the bottom of lift conduit 18 is positioned exteriorly of the pressure supply vessel, and in that lifting ga is introduced into vessel 16 at the top of the latter, rather than through a side channel. In both cases, as is preferred according to the invention, lifting gas passes, before entering the restricted downflow conduit, through a solids mass in vessel 16 having expanded cross section relative to the cross section of the Turning now to Figure 4: there is shown an engaging vessel 16, lift conduit 18, solids inlet line 33, gas inlet line 30, channel 35, disk 36, rod 37, and cylindrical sleeve 39 closed ofi at the bottom by disk 36 and surrounding and spaced apart from a lower portion of lift conduit 18. In operation, vessel 16 receives solids through line 33 and lifting gas under elevated pressure through line 30 and channel 35. Lifting gas is introduced through the dense mass of solids in vessel 16 into and through the annular dense mass of solids descending between sleeve 39 and lift conduit 18, and is introduced into the bottom of lift conduit 18. Lifting gas thus introduced causes the solids to rise in 'a dense mass through lift conduit 18, and more solids are continuously introduced under elevated pressure through the space between sleeve 39 and lift conduit 18 and into the bottom of lift conduit 18.

The annulus between sleeve 39 and lift conduit 18 contstitutes a restricted downflow conduit communicating through a closed connection with a restricted horizontal inlet to lift conduit 18. Preferably, according to the invention, the cross sectional area of the path through the annulus and into the lift conduit is approximately equal to the horizontal cross section of the bottom of the lift conduit.

Turning now to Figure 5: there are shown disengager 19, lift conduit 18 having its upper end positioned within disengager 19, gas outlet 20, solids outlet'21, sleeve 40 around and spaced apart from lift conduit 18, bottomj plate 41closing off the bottomof sleeve 40, top plate. 42 closing off the top of sleeve 40 and having a central ass sts-s the top thereof, apertures 47 thereth'rough, providing communication between the interior of lift conduit 18 and the interior of sleeve 40.

In operation, adense mass of granular contact material rises through lift conduit 18, being impelled by lifting gas. As the dense mass passes the a'pertured area, a portion oft'he lifting gas in the dense mass dissociates therefrom and passes through the apertures 47 into the sleeve 40 and therefrom through line 43. The rate of withdrawal of lifting gas from the dense mass can be controlled by means of the valve 48. V acuum-producing rneans'can, if desired, be associated with line 43. That part of the lifting gas which does not pass out through the apertures 47 passes upwardly with the dense mass of contact material which rises above the apertures 47, through the annular space between the lift conduit walls and the bathe 44, and into the enlarged space provided by the interior of disengager 19. The solids reverse direction and gravitate through disengager 19 as a compact mass into line 21 The lifting gas discharged into the disengager 19 disengages from the solids and leaves disengager 19 through line 20 and can be conveyed to suitable means not shown, e. g. a cyclone separator, for rein'oving fine particles of contact material which may be entrained therewith. The lifting gas removed through the apertures 47 and sleeve 40 can also be conveyed through line 43 to such means for removing fines. The apertures 47 are preferably small enough to prevent coarse solids from passing therethrough, but fine particles may pass therethrough entrained by the lifting gas. The apertures 47 provide an apertured area in the sidewall of lift conduit 18. According to the present invention such apertured area is preferably provided'at a distance from the top of the lift conduit within the approxi mate range 0.5-5 times the major dimension of the cross section of the top of the lift conduit. The sleeve 40, with its bottom and top closing plates 41 and 42, and gas outlet 43 constitute means for regulating the amount of lifting gas withdrawn through the apertures 47. Other suitable means can be used according to the present in-.

vention.

The conical baffle 44 provides means for restricting the cross sectional area available for passage of solids through the lift conduit near the top thereof to an area less than the average cross sectional area of the entire lift conduit. Other suitable means for accomplishing this result canbe used' according to the present invention. ""Preferably, conical baffle 44 has its apex positioned at such a level'below'the top of lift conduit '18, and the heightof the baffle 44 relative to the base diameter thereof is such that the cross sectional area available for solids passage at the top of the lift conduit is within the approximate range' 0.3-0.9 times the average cross section of the lift conduit. Also, preferably, the available cross section gradually decreases, as in the apparatus shown in Figure 5, toward the top of the lift conduit, the vertical length of'the section through which the decrease in cross section occurs being preferably not substantially greater than twice the major dimension of the average horizontal cross section of-the lift conduit.

"The apparatus shown in Figure 5 is used with particular advantage according to the present invention in that it tends to stabilize the dense phase lifting operation and prevent it from becoming "a sparse'phase lifting operation through increased velocity of solids travel. Although the invention is'not to belimited by any theory, it is 'oe-' lievedt hat removing lifting gas through the ap'ertures 47 causes the solids rising above the apertures tohave less velocity than they would have if lifting gas were not thus removed, so thatthe tendency for' solids to issue too rapidly from the top of the lift conduit is thus reduced. Also, it isbelieved that the reduction of the cross section at the top of the lift conduit, as by means of baffie 44 for example, causes a'braking action to be exerted on the dense mass of solids.

The following example illustrates the invention: A dense phase lifting operation was carried out in apparatus having" the features of the present invention. A cylindiical engaging vessel 16 inches in diameter and about 36 inches high and having a solids inlet at the top thereof was used'ythis vessel was similar to vessel 16 as shown in Figure 1. A two-inch vertical cylindrical lift conduit communicated withthe vessel and had its lower intake end positioned about 12 inches from the bottom of the vessel. Secured to the lower end of the lift conduit was a 180 pipe bend having a 2 inch pipe section one inch in length secured to its open end. The pipe section and the open-end half of the pipe bend constituted a downflow conduit for granular solids. The lift conduit was 14 feet high and its upper end communicated with a disengaging vessel. Associated with the top of the lift conduit were means generally similar to those shown in Figure 5 for controlling the flow of solids and lifting gas from the lift conduit. An inverted cone having a 2- inch diameter base and a height of 3 inches was positioned concentrically with the lift conduit. A cylindrical sleeve was slidably mounted around the top of the lift conduit in frictional contact therewith, the top of the sleeve being about 3 inches above the top of the lift conduit. The sleeve had an apertured area provided by circular holes drilled through the wall of the sleeve, the holes being spaced vertically apart and also spaced around the periphery'of the sleeve'in the region between about 2.5 to 3 inches from the top of the sleeve. The apex ofthe cone was positioned about 0.5 inchbelow the topof the sleeve.

In this embodiment of the invention, the apertured sleeve constitutes a movable apertured portion ofthe lift conduit, and also constitutes means for controlling the amount of lifting gas removed through the apertured area, the relative positions of the sleeve and the unapertured portion of. the lift conduit determining the number of apertures through which lifting gas can escape.

The engaging vessel was filled while at atmospheric pressure with a mixture of granular beads of cracking catalyst. The lift conduit was also filled from the top with the same mixture of beads. Substantially all of thev beads in the mixture were small enough to pass a 3 mesh U. S. Sieve Series. screen; a screen analysis of a sample of the mixture is asfollows:

Weight Passes Is Re- Percent' tained' On 69. 2 6 mesh 28. 7 6 mesh 8 mesh 1. 4 8 mesh 10 mesh 0. 4 10 mesh 12 mesh 0. 2 12 mesh 14 mesh 0. 05 14 mesh 16 mesh 0. 05 16 mesh pounds of the beads.

Thesolids inlet to the engaging vessel was closed off by a valve, and lifting air was introduced at about'lO pounds per square inch gauge pressure and at a rate of about 19.5 standard cubic feet per minute into an annular r space at the periphery of the vessel providedby a circular channel arrangedsimilarly to channel 35 in Figure 1. The air passed around the lower edge of the channel, which was about 4 inches beneath the lower end of the lift conduit and about 6 inches horizontal distance from the centerline of the lift conduit, and into the compact bed of catalyst. The air passed upwardly through the catalyst to the intake end of the pipe section, then downwardly thereinto for concurrent flow with catalyst through the pipe section, pipe bend, and lift conduit. Catalyst issued continuously from the top of the lift conduit as a dense mass which rose a maximum of only a few inches above the top of the lift conduit before falling into the bottom of the disengager. The catalyst rate was about 1.04 tons per hour. The operation continued smoothly until the catalyst level in the engaging vessel dropped to the point where no more catalyst flowed into the intake end of the pipe bend. Upon abrupt interruption of the lifting gas supply, and after the solids came to rest, the solids completely filled the lift conduit, indicating a high concentration of solids and low solids velocity in the lift conduit during the lifting operation.

In a dense phase lifting operation similar to the above but with an air rate of 26 standard cubic feet per minute, the catalyst rate was increased to about 1.87 tons per hour. Increasing the air rate above 26 feet per minute resulted, under the other conditions prevailing, in a sparse phase rather than dense phase lift.

This example shows that operation according to the invention provides a smoothly functioning dense phase lift operation with very low height of rise and accordingly a low degree of attrition.

It is noted that in the preceding example, a maximum lifting gas rate for dense phase operation was found to exist between 19.5 and 26 standard cubic feet per minute. This maximum rate varies widely with the other conditions in the lifting operation e. g. dimensions of lift, size of solids, etc. In the light of the present specification, a person skilled in the art can readily determine the maxi mum gas rate for any given set of other conditions.

It is to be understood that the particular apparatus features associated with the disengager, as illustrated in Figure 5, though particularly useful in some operations to increase the stability of the operation, may in some instances be unnecessary, the operation being stable enough without such apparatus features. Such instances may occur, for example, where the distance through which the solids are elevated is relatively high, e. g. more than 100 times the average major dimension of the horizontal cross section of the lift conduit, so that the weight of solids in the lift conduit provides suificient braking action on the lifting gas to prevent the operation from becoming a sparse phase rather than a dense phase lift.

The invention claimed is:

1. Method for continuously elevating a mixture of granular solids a major proportion of which are coarse particles too large to pass through a 20 mesh screen which comprises: supplying such granular solids as a compact mass to :a lower inlet of an elongated confined lifting zone containing a dense mass of such granular solids; flowing lifting gas under elevated pressure through said compact mass to said inlet and thence through said lifting zone at a rate adapted to maintain the solids in dense form, thereby to move said solids upwardly through said lifting zone as a dense mass propelled by lifting gas; transporting said solids through an upper portion of said lifting zone as an annular mass having gradually upwardly decreasing cross-sectional area while deflecting all of said solids radially outwardly in a circumferentially complete path and permitting unobstructed flow of said solids in an upwardly inclined direction; discharging said solids from said upper portion into an expanded zone; decelerating said solids by disengaging lifting gas while permitting unobstructed flow of said solids in an upwardly inclined direction; and collecting said solids, after reversal of vertical direction of flow, in a lower portion of said expanded zone.

2. Method according to claim 1 wherein the crosssectional area of said annular mass at a given horizontal level is changed during said elevating.

3. Method according to claim 1 wherein a portion of the lifting gas rising through said confined lifting zone is removed therefrom substantially separately from coarse solids, and the distance between the location of removal of said portion of lifting gas and the upper end of said lifting zone is within the approximate range from 0.5 to

5 times the major dimension of the cross section of the top of said lifting zone.

4. Method according to claim 1 wherein the crosssectional area of said annular mass at the upper end of said lifting zone is within the approximate range from 0.3 to 0.9 times the average cross-sectional area of said lifting zone.

5. Method according to claim 1 wherein the length of said upper portion is not substantially greater than twice the major dimension of the average horizontal cross section of said lifting zone.

6. Method according to claim 1 wherein said supply:

ing is effected by passing solids and lifting gas down wardly through a relatively enlarged zone, then through a relatively restricted zone, reversing direction of solids and lifting gas in a restricted zone, and introducing solids and lifting gas into the lower end of said confined lifting zone.

. 7. Method according to claim 1 wherein a portion of the lifting gas rising through said confined lifting zone is removed therefrom, adjacent and below the upper end thereof, substantially separately from coarse solids, and wherein granular solids and the remainder of the lifting gas are discharged from the upper end of said confined lifting zone.

8. Method according to claim 1 wherein said granular solids comprise a siliceous hydrocarbon conversion catalyst.

9. Method for elevating a mixture of granular solids a major proportion of which are coarse particles too large to pass through a 20 mesh U. S. Sieve Series screen which comprises: establishing a compact mass of such granular solids within an elongated confined lifting zone communicating through a lower inlet thereof with a solids supply zone containing a compact bed of such granular solids; subsequently initiating the supply of lifting gas to said lower inlet of said lifting zone; and flowing lifting gas under elevated pressure through said compact bed and thence through said lower inlet into and through said lifting zone at a rate adapted to maintain the granular solids in said lifting zone in dense form, thereby to move granular solids from said compact bed through said lower inlet into said lifting zone and to move granular solids upwardly through said lifting zone as a dense mass; transporting said solids through an upper portion of said lifting zone as an annular mass having gradually upwardly decreasing cross-sectional area while deflecting all of said solids radially outwardly in a circumferentially complete path and permitting unobstructed flow of said solids in an upwardly inclined direction; discharging said solids from said upper portion into an expanded zone; decelerating said solids by disengaging lifting gas while permitting unobstructed flow of said solids in an upwardly inclined direction; and collecting said solids, after reversal of vertical direction of flow, in a lower portion of said expanded zone.

10. Apparatus for continuously elevating granular solids which comprises: an engaging vessel; a lift conduit in communication with said engaging vessel and extending upwardly therefrom; a transverse baffle having an upper, horizontal, plane surface and positioned within said engaging vessel and beneath and spaced apart from the lower end of said lift conduit; means for moving said baflie in a vertical direction within said engaging vessel; means for introducing granular solids and lifting gas into said engaging vessel; and a disengaging vessel communieating with the upper end of said lift conduit.

lower end by said battle and. being open at its upper end,

12. Apparatus, for continuously elevating granular solids which comprises: an engaging vessel; a lift conduit in 1 communication with said engaging vessel and, extending upwardly therefrom, said lift conduit having an apertured area adjacent and belowthe upper end thereof; means for introducinggranular solids and lifting gas into said engaging vessel; a disengaging vessel communicating with the upper end of said lift conduit; and a downwardly tapered baffle positioned within said disengaging vessel arnl having its lower end extending downward into the upperendof said lift conduit.

13. Apparatus according to claim 12 and additionally comprising means for varying the cross-sectional area of said lift conduit adjacent the upper end the reof, said area being less than the verage cross-sectional area of the lift conduit.

14. Apparatus according to claim l2 wherein the distance betweensaid apertured area and the upper end of said" lift conduit is within the approximate range from 0.5 to 5 times the major dimension of the cross section of the topof said lift conduit.

15; Apparatus according toclaim l2 whereinthe crosssectional area of the annular space between said battle and said lift conduit at the upper end of said lift conduit is within the approximate range from 0.3 to 0.9 times the average cross-sectional area of said lift conduit.

16, Apparatus according to claim 12 wherein the distance between the lower end of said bafile and the upper end of saidlift conduit is not substantially greater than twice'the major dimension of the average horizontal cross section of said lift conduit.

17. Apparatus according to claim 12 and additionally comprising adownfiow conduit having a lower portion communicating through a connecting conduit with the lower end of,said lift conduit and having its upper end communicating with the interior of said engaging vessel.

References Cited in the file of this patent UNITED STATES PATENTS 494,274 Kelley Marl28, 1 893 a 727,030 Tilghman May 5, 1903 1,597,438 Ennis Aug. 24, 1926 1,846,069 Schaub Feb. 23, 1932 2,304,827 Jewell Dec. 15, 1942 2,541,077 Letfer- Feb. 13, 1951 2,684,867 Berg fi July 27, 1954 2,684,872 Berg July 27, 1954 2,684,928 Berg- July 27, 1954 2,693,395 Berg- Nov. 2, 1954 2,694,605 Berg Nov. .16, 1954 FOREIGN. PATENTS 180,397 GreatBritain May 11, 1922 268,667"

Great Britain Apr. 7, 1927. 

1. METHOD FOR CONTINUOUSLY ELEVATION A MIXTURE OF GRANULAR SOLIDS A MAJOR PROPORTION OF WHICH ARE COARSE PARTICLES TOO LARGE TO PASS THROUGH A 20 MESH SCREEN WHICH COMPRISES: SUPPLYING SUCH GRANULAR SOLIDS AS XXXMPACT MASS TO A LOWER INLET OF AN ELONGATED LIFTING ZONE CONTAINING A DENSE MASS OF SUCH GRANULAR SOLIDS; FLOWING LIFTING GAS UNDER ELEVATED PRESSURE THROUGH SAID COMPACT MASS TO SAID INLET AND THENCE THROUGH SAID LIFTING ZONE AT A RATE ADAPTED TO MAINTAIN THE SOLIDS IN DENSE FORM, THEREBY TO MOVE SAID SOLIDS UPWARDLY THROUGH SAID LIFTING ZONE AS A DENSE MASS PROPELLED BY LIFTING GAS; TRANSPORTING SAID SOLIDS THROUGH AN UPPER PORTION OF SAID LIFTING ZONE AS AN ANNULAR MASS HAVING GRADUALLY UPWARDLY DECREASING CROSS-SECTIONAL AREA WHILE DEFLECTING ALL OF 